Alien Registration- Gallant, John H. (Brewer, Penobscot County)

https://digitalmaine.com/alien_docs/11132/thumbnail.jp

Particle Acceleration at Ultra-Relativistic Shocks and the Spectra of Relativistic Fireballs

We examine Fermi-type acceleration at relativistic shocks, and distinguish between the initial boost of the first shock crossing cycle, where the energy gain per particle can be very large, and the Fermi process proper with repeated shock crossings, in which the typical energy gain is of order unity. We calculate by means of numerical simulations the spectrum and angular distribution of particles accelerated by this Fermi process, in particular in the case where particle dynamics can be approximated as small-angle scattering. We show that synchrotron emission from electrons or positrons accelerated by this process can account remarkably well for the observed power-law spectra of GRB afterglows and Crab-like supernova remnants. In the context of a decelerating relativistic fireball, we calculate the maximum particle energy attainable by acceleration at the external blast wave, and discuss the minimum energy for this acceleration process and its consequences for the observed spectrum.Comment: To appear in Proceedings of the 5th Huntsville Gamma-Ray Burst Symposium. LaTeX, 6 pages, 2 figures, uses aipproc.sty and epsfi

An eigenfunction method for particle acceleration at ultra-relativistic shocks

We adapt and modify the eigenfunction method of computing the power-law spectrum of particles accelerated at a relativistic shock front via the first-order Fermi process (Kirk, J.G., Schneider, P., Astrophysical Journal 315, 425 (1987)) to apply to shocks of arbitrarily high Lorentz factor. The power-law index of accelerated particles undergoing isotropic small-angle scattering at an ultrarelativistic, unmagnetized shock is found to be s=4.23 +/- 0.2 (where s=d\ln f/ d\ln p, with f the Lorentz-invariant phase-space density and p the momentum), in agreement with the results of Monte-Carlo simulations. We present results for shocks in plasmas with different equations of state and for Lorentz factors ranging from 5 to infinity.Comment: 4 pages, 2 figures, contribution to the Proceedings of the 5th Huntsville GRB Symposiu

On finding minimal length superstrings

AbstractA superstring of a set of strings {s1,…, sn} is a string s containing each si, 1 ⩽ i ⩽ n, as a substring. The superstring problem is: Given a set S of strings and a positive integer K, does S have a superstring of length K? The superstring problem has applications to data storage; specifically, data compression. We consider the complexity of the superstring problem. NP-completeness results dealing with sets of strings over both finite and infinite alphabets are presented. Also, for a restricted version of the superstring problem, a linear time algorithm is given

Vision and its Relationship to Novel Behaviour in St. Lawrence River Greenland Sharks, Somniosus microcephalus

Rarely observed Greenland Sharks, Somniosus microcephalus, were recorded at shallow depths by divers employing underwater video in the St. Lawrence River, in association with a seasonal concentration of Capelin (Mallotus villosus) in May-June 2003. We recorded unique proximity-induced display motor patterns in these sharks, which have not been recorded in underwater observations of Arctic Greenland Sharks. Arctic sharks have a high incidence of blindness due to an ocular copepod parasite, Ommatokoita elongata. The absence of parasite-induced blindness in St. Lawrence Greenland Sharks, in contrast to endemic blindness in the Arctic population, may allow sharks in this region to more readily visually recognize the presence of conspecifics and potential prey. Improved visual acuity may therefore allow St. Lawrence River sharks to express a different behavioural repertoire than Arctic sharks, with resulting changes in intra- and inter-specific aggression and predatory behaviour

Chandra Observations of the Crab-like Supernova Remnant G21.5-0.9

Chandra observations of the Crab-like supernova remnant G21.5-0.9 reveal a compact central core and spectral variations indicative of synchrotron burn-off of higher energy electrons in the inner nebula. The central core is slightly extended, perhaps indicating the presence of an inner wind-shock nebula surrounding the pulsar. No pulsations are observed from the central region, yielding an upper limit of ~40% for the pulsed fraction. A faint outer shell may be the first evidence of the expanding ejecta and blast wave formed in the initial explosion, indicating a composite nature for G21.5-0.9.Comment: 4 pages, 2 figures, formatted with emulateapj, submitted to ApJ

Exile Vol. III No. 1

The Dreamer by Jesse Matlack 8-11 And Now a Response by John Kenower 12-16 Two Scenes from a Play by Robert Whitlatch 17-21 The Urgency of the Situation by Jim Gallant 22-23 James Branch Cabell by Robert Canary 24-29 Was Rasselt Im Stroh by Carol Dugle 30-31 Three Stops for an Artist by Nicos Stangos 32-36 POETRY Of Darkness by Burnell Chaney 16 Wolf in Sheep\u27s Clothing by Ellen Moore 21 Fresh Snow OR The Stars Have Fallen by Thomas Turnbull 29 When I Left Home by Yoko Kuyama 37 Standing Under a Tall Bare Tree by Yoko Kuyama 38 I Have Been Alone Too Long by Ellen Moore 40 Dirge: For Myself by Ellen Moore 40 In this issue the editors of EXILE are proud to publish Three Stops for an Artist by Nicos Stangos. This story has been awarded the semi-annual Denison Book Store - EXILE Creative Writing Prize